Answer
$21x^{5}y^{}z^{4}$
Work Step by Step
RECALL:
The product rule of exponents states that: $a^m \cdot a^n=a^{m+n}$.
Multiply the numerical coefficients, and use the rule above to find:
$\\=21x^{4+1}y^{0+1}z^{1+3}
\\=21x^{5}y^{1}z^{4}
\\=21x^{5}y^{}z^{4}$
